I have recommended Susan Lewis on here a number of times before, and promise I'm not on commission, but I really rate her as a trainer! I am 6ft 2 with three young children so my posture really suffers. My sessions with Susan have really helped me to realign and focus on my posture. She is a LOVELY lady who has two daughters, one of whom is around the same age as yours, so although I only have experience of her training me, I imagine that she'd be fantastic with your daughter. Even if your daughter is not sporty as such I think Susan could have a real impact on her. Maybe just give her a call to chat through whether she could help. Being a very tall teen I spent years bent over to be the same height as my peers so wish I'd had the confidence I have now to stand tall. It's great that you are looking to help your daughter now if she is doing a similar thing. Good luck.
http://www.bammuk.com/about.html